ASHEVILLE, N.C. -- Police Officer Robert Bingaman was driving at an estimated 70 mph in a 50 mph zone and wasn't wearing his seatbelt when his cruiser hit a guardrail and went over the side of Jeff Bowen Bridge, authorities said Friday.

Bingaman, 37, died in the Oct. 29 crash after the vehicle plummeted at least 50 feet and struck an embankment, coming to rest against a bridge column near the French Broad River.

A report on the N.C. Highway Patrol's investigation of the accident said the officer was headed west on Interstate 240 when he swerved left to avoid traffic. The cruiser hit the guardrail and rotated counter-clockwise.

"The rear of the vehicle lost contact with the ground and traveled upon the guardrail, continuing onto the bridge rail," the report states. The car "rolled over the bridge rail and struck the ground below."

The estimated speed at impact with the guardrail was 68 mph, according to the report. No one else was hurt. A Highway Patrol reconstruction team investigated the crash.

Police Chief William Anderson said in a recording released Friday that he shared the results of the investigation with Bingaman's family and APD officers on Thursday.

Investigators concluded Bingaman "was traveling at a speed of 70 mph and was not wearing his seatbelt," he said.

The wreck happened around 1 p.m. Witnesses said the patrol car's blue lights were not on. The city has not yet released dispatch logs and radio traffic requested under public records law.

"We may never know exactly what happened leading up to this accident," Anderson said. "But we do know Officer Bingaman was assigned to work traffic in an area known for vehicular crashes.

"Officer Bingaman was an outstanding officer who came to work every day with the will to serve."

Anderson did not respond to a question about whether Bingaman was responding to a call.

Sgt. Dave Romick, the department's spokesman, said police officials would make no further comments about the wreck.

Bingaman, a six-year veteran of the force and ex-Marine, was the first Asheville officer killed in the line of duty in 41 years. He was a member of the traffic safety unit.

He left behind a wife, Genevieve Bingaman, three teenage stepdaughters and extended family in Pennsylvania.

"We will learn everything we can from this tragedy and will be a better department in the end," Anderson said. "I believe this is what Rob would want us to do."

Bowen Bridge is the busiest stretch of road in the state west of Gaston County, according to the state Department of Transportation. It carried an average of 99,000 vehicles a day last year.